In this article will be on how to check if a given value is a number or NaN (Not-a-number).
In programming language, a number is a datatype that denotes a integer or a floating point. And a String can be define as a sequence of character which includes both letters and numbers. Example: “Hello”, “123abc” etc.
So let’s check how we can find if a string consist only number using the method below:
Using isNaN() to check if a JavaScript String has a Number.
The isNaN()
function determine whether a given value is a number or NaN (Not-a-Number).
If the output returns true, that means it’s NaN value and if it’s false, it’s a valid number.
Syntax:
isNaN(value)
Example:
console.log(isNaN('2022')) // false
console.log(isNaN('computer')) // true
console.log(isNaN('123abc')) // true
We can write a function isNumber() that will return true if the string is a number.
function isNumber(val){
if(isNaN(val)) {
return false
}
return true
}
console.log(isNumber('2022')); // true
console.log(isNumber('computer')); // false
console.log(isNumber('123abc')); //false
Using Number() function to check if a string is a number
The Number()
function convert a given value of other datatype (eg: string etc) to a number representing the object ‘s value.
Syntax:
new Number(value)
It will return number if the string contains only number or else it will return NaN (Not-a-Number).
Example:
console.log(Number('2022')) // true
console.log(Number('hello')) //NaN
console.log(Number('123abc')) //NaN
Using Unary Plus (+) operation to determine whether a string is numeric in JavaScript
The +
operator coverts a string to a number. It will return the number value of the string or else it will return NaN (Not-a-Number) if the given value is not a pure number.
Example:
console.log(+'2022') // 2022
console.log(+'hello') // NaN
console.log(+'abc123') //NaN
Related Topics:
Check if a value is a number in JavaScript
How to compare two strings in JavaScript?
How To Check Null Values In JavaScript?
JavaScript – Detect if a string contains any space
Check if String starts with a space in JavaScript